This invention is directed toward the art of joints and couplings. More particularly, the invention relates to an apparatus for testing the adequacy of swaging of tubes or pipes.
The present invention is especially suited for use in testing the adequacy of pull up of ferrules of swage type tube fittings on tubes or pipes and hence the adequacy of the swaging operation and will be described with particular reference thereto. It should, however, be appreciated that the subject invention is capable of broader applications and could be used for testing the adequacy of pull up of ferrules onto cylindrical members that are used for many different purposes.
Swage type tube or pipe fittings have become widely used. These fittings generally employ one or more ferrules which encircle the tube or pipe to be coupled. As the coupling nut is advanced on the coupling body, the ferrule or ferrules are subjected to axial pressure and are forced into a tapered mouth in the coupling body thereby causing the ferrule to contract upon the tube or pipe. In this way, the ferrule is progressively deformed into a gripping and sealing engagement with the tube or pipe by a radial contraction of the ferrule due to the interaction of the coupling nut and the fitting body. Since the contraction of the ferrule upon the tube or pipe is produced by an advancement of the coupling nut along the coupling body, it is apparent that the amount of contraction of the ferrule is determined by the amount of advancement of the coupling nut.
To a considerable extent, the successful utilization of couplings of the aforementioned type depends upon a controlled constriction or swaging of the walls of the tubular member to be coupled. In fittings of this type, the optimal amount of tube wall constriction or swaging is a predetermined quantity depending upon the correct amount of linear nut advancement necessary to produce the optimum amount of swaging. If the coupling nut is not advanced far enough, the ferrules will not be contracted or collapsed sufficiently to produce the required swaging of the tube wall. An insufficient swaging results in a connection which is susceptible to leakage. On the other hand, should the coupling nut be advanced more than the prescribed amount, the annular ferrules will be overcontracted upon the tube wall causing an overswaging of the tube. Such excessive swaging may result in reducing the number of times that the fitting can be disconnected and remade. It can also cause a rupture of the tubular member wall or at least create fluid flow problems in the tubular member.
In making an effective and tight connection between a tube or pipe in this type of fitting, it is also important that the dimensional relationships between the tube or pipe and the various components of the fitting not vary appreciably from those prescribed. Deviations from the prescribed tolerances on the amount of radial contraction of the ferrules onto the tube or pipe to create a clinching grip on the tube or pipe may result in unsatisfactory connections leading to inadequate sealing and leakage.
While there have been some devices which measure the amount of swaging or tube deformation that has occurred between a cylindrical body and a fitting, none of these has been found to be fast, easy to use and precise in its readout of the adequacy of swaging. Also, none of the current measuring devices can be selectively recalibrated as desired. Further, none of the current measuring devices are provided with a master to check the accuracy of the readings provided by the measuring device.
Accordingly, it has been considered desirable to develop a new and improved device for measuring the adequacy of swaging which would overcome the foregoing difficulties and others while providing better and more advantageous overall results.